In recent years, as the performance of vehicles have been improved, chiefly in order to improve the side rigidity of the tires, flatter tires have been developed. On the other hand, an increase in the flatness of tires increases the diameter of the tires and induces separations starting at ends of the tire belts, thus reducing the durability of the tires.
As a technique for suppressing the increase in the diameter of a tire, providing one or more circumferential belt layers obtained by rubber-coating cords substantially extending in the tread circumferential direction is known (for example, see JP 2000-062411 A (PTL 1), JP 2009-184371 A (PTL 2), and JP 2009-126363 A (PTL 3). Here, the circumferential belt layer has a hooping effect in suppressing the protrusion in the tire radial direction due to the internal pressure or the rotation of the tire, which suppresses the increase in the tire diameter and accordingly improves the durability of the tire.
There are attempts to increase the width of a circumferential belt layer in the tire width direction thereby preventing uneven wear of a tire by increasing the rigidity of the tread and further improving the durability of the tire by suppressing the increase in the diameter in regions on the ground contact end side of the tread (see PTLs 2 and 3, respectively).
In general, the tread surface of a tire is provided with a plurality of circumferential grooves extending in the tread circumferential direction, and shoulder land portions are partitioned between the circumferential grooves located outermost in the tire width direction and ones on the tread ground contact ends.
Therefore, in a pneumatic tire having a circumferential belt layer with an increased width as described above, the outermost ends in the tire width direction of the circumferential belt layer often extend to positions in the tire width direction where the shoulder land portions are provided.